This invention relates to fire-fighting foam generating apparatus and more particularly to such apparatus which includes an elongated housing having an inlet and outlet, a net member extending across its passage area, a fan to propel air through the housing, and a plurality of reaction nozzles mounted on a fan rotor for spraying foam producing solution onto the net member and for driving the fan rotor by the reaction forces thus produced to pump air outwardly through the net member to generate the foam.
It has heretofore been known in the art that the efficiency of a water powered apparatus depends upon the percentage of the power available in the water supply which is utilized to produce the air flow through the apparatus, and upon the uniformity of the distribution over the surface of the net member, of both this air flow and the solution used by the apparatus.
It has also been known in the art that when both air flow and the solution are evenly distributed over the surface of the net, the foam produced at all points on the net will contain the same ratio of the solution to air. The quantities of air and solution can then be selected so that all of the foam produced will have the proper ratio of solution to air for maximum effectiveness in fire-fighting.
In order to achieve maximum utilization of the available water power, all of the nozzles are required to be mounted at the greatest possible distance from the shaft to provide the largest moment arm.
On the other hand, the radial distance at which the reaction nozzles are positioned from the axis of the shaft must also be a compromise. If the nozzles are positioned at a substantial radial distance from the shaft to increase the power extracted from the water, then the solution issuing therefrom is directed toward the outer edge of the net to an even greater extent as would defeat the purpose of uniformity. If the nozzles are positioned close to the axis of the shaft to increase the distribution of this solution over the net, then the amount of power extracted from the water is reduced.
In addition, the distribution of the solution over the net is seriously hampered by the centrifugal force acting upon the solution issuing from the reaction nozzles because of the rotation of these nozzles. This centrifugal force tends to throw the solution outwardly thus further concentrating the solution at the outer edge of the net.
The above mentioned two optimum conditions cannot coexist in a workable unit of the prior art type. This is now a problem and solution is demanded.